I saw an immature tern in flight on May 21, and what I presume was the same tern perched on May 22. The first day, I thought it was a Forster's Tern (the black patch through the eye but not around the back of the head). The next day, I found what was likely the same tern perched, and I saw that it had a carpal bar which a Forster's Tern isn't supposed to have. Then I thought it must be a Common Tern, but with barely any black at the back of the head, I wonder if there's any chance it could be a Least Tern. Can anyone tell from the pictures I posted below?